When Juana Burns, now 20, decided to hold auditions for a new rap group last year, she was startled to open the front door of her family's Rialto, Calif., house and find her old neighborhood pal Dania Birks, now 15, standing there. "I watched her grow up," says Burns. "I remember when she was in diapers. I'd never have believed she'd be beat-boxing with me." Surprise! Birks won the job. Three months later Michelle "Chelly" Franklin, 19, rapped on the door. She had no experience, but she'd just made up a rap at a party and decided she was good. Surprise again—she got the job too. Surprise No. 3: Today, calling themselves M.C.J.B., Baby-D. and Sassy C. and their trio J.J. Fad, the girls are the newest stars of rap. Their first single, "Supersonic," recently topped Billboard's dance sales chart; their Supersonic album is 49 on the album charts and rising fast; and the trio has been the opening act on Run-DMC's tour—clearly an initial attraction.

The girls are excited but not exactly bowled over by their excess success.

"Friends just dared me to rap, so I did, and now we do," says M.C.J.B.

"Me and J.J. Fad are just a case of being in the right place at the right time," Sassy C. explains.

J.J. Fad, like the duo DJ Jazzy Jeff & the Fresh Prince, is part of a startling new breed of rappers: As clean-cut as can be, the three are into bowling, pin-ball and miniature golf, don't smoke or do drugs, and boast that their favorite drinks are virgin daiquiris. They're even humble. "We're all more careful with old friends now, like getting back to them right away when they call," M.C.J.B. says. "I don't want them to feel they're not important just because we have a hit song." M.C.J.B.'s mom does admit her little girl had moments of star behavior. "She started getting sassy, like she was running this house, but she settled down," Virginia Burns says. "I told her to stop chasing rainbows and get a 9-to-5 job, but I should have known she'd find a way to slide into that pot of gold. She even bought me a big 50-inch TV for Mother's Day." Or, as Baby-D. raps on Supersonic: "We are the home chicks who are rockin' your world."